1. Field of the Invention
The present invention belongs to the optical invisibility material technical field, which relates to a mechanical chameleon by using dynamic real-time plasmonic tuning.
2. Description of the Related Art
Optical invisibility represents one of the greatest challenges in military and biomimetic research. Despite tremendous efforts, the camouflage methods under study today are mostly derived from pattern painting dated to 1940s. A more sophisticated approach involves the redirection of the incident light to develop an “invisibility cloak” It was only recently that the metamaterials have proved effective in bending electromagnetic waves in the microwave region, but extending to the entire visible spectrum for practical use has been challenging, especially in surroundings that support ballistic light propagation. On the other hand, active camouflage that rapidly adapts the surroundings of an object such as a chameleon could be more feasible to achieve effective invisibility. The key to this biomimetic technology is realizing electrically-driven actuation of broad reflection bands, which may be partially enabled by some of the existing approaches, including electrophoretic, cholesteric liquid crystalline, and electrochromic. The main drawback of these technologies is that they often need color filters or multiple color-mixing layers, thereby resulting insubstantially low reflectivity and more complexed devices. Despite the report of single layered devices such as photonic crystals, their multi-coloration capability is still in their infancy. Nevertheless, their thermal expansion and contraction may severely influence the coloration in an environment with a fluctuating temperature due to the inherent dependence of reflection wavelength on the interparticle separation. It is well known that plasmonic nanostructures can be utilized to drastically tune optical reflection and absorption in the range of ultraviolet-to-near-infrared region. They also have been demonstrated to produce more saturated colors than standard technologies, albeit the difficulty in attaining electrically actuatable colors.